Anatomic Osteochondral Allograft Reconstruction for Concomitant Large Hill–Sachs and Reverse Hill–Sachs Lesions

Glenohumeral instability causing bipolar bone loss is increasingly being recognized and treated to minimize recurrence. Large Hill–Sachs and reverse Hill–Sachs lesions of the humerus must be addressed at the time of surgery to prevent recurrent dislocations and restore the native anatomic track. For patients with epilepsy, locked dislocations may create defects that must be addressed with bony procedures, including osteochondral allograft reconstruction as soft-tissue remplissage may not adequately addresses the magnitude of the bone loss. Osteochondral allografts have been successfully used to address bony defects ranging from 20% to 30% of humeral bone loss whereas shoulder arthroplasty is indicated for larger defects where the native anatomy can no longer be restored. In this Technical Note, we present a technique to address concomitant large Hill–Sachs and reverse Hill–Sachs lesions.

A nterior shoulder instability impacts approximately 1 per 1,000 patients annually in high-risk cohorts, for example, in contact athletes and military patients. 1 While anterior shoulder dislocations account for greater than 90% of glenohumeral instability, posterior dislocations are increasingly being recognized. 2 Specific subsets, including those patients with epilepsy, are at increased risk for posterior glenohumeral instability. 3 While arthroscopic capsulolabral repair for isolated anterior and posterior labral injuries has been described extensively, 4 recurrent instability with consequent bipolar bone loss often necessitates different treatment options. Posterior dislocations with less than 20% humeral bone loss in reverse HilleSachs lesions have been treated successfully with reduction and subscapularis remplissage, 5 the McLaughlin procedure, or modified McLaughlin procedure. Greater amounts of bone loss may be better treated with osteochondral allograft reconstruction to restore the native anatomy. 6 Similarly, although arthroscopic labral repair with infraspinatus remplissage has been described extensively for anterior shoulder instability with minimal bone loss, 7 locked dislocations with large HilleSachs lesions also may benefit from osteoarticular reconstruction. 8 Here, we present a technique for humeral head osteochondral allograft reconstruction for concomitant HilleSachs and reverse HilleSachs lesions (Video 1).

Surgical Technique (With Video Illustration)
Preoperative imaging of the patient in this case example shows large HilleSachs and reverse HilleSachs lesions of the left shoulder without significant glenoid bone loss (Fig 1). A standard deltopectoral approach is performed. The superior one-third of the pectoralis major tendon is released from its insertion on the humeral to aid in exposure. A subscapularis peel is performed by releasing the tendon off of its insertion on the lesser tuberosity. Care is taken to coagulate the anterior humeral circumflex vessels at the inferior border of the subscapularis. The inferior capsule is released from the humeral head to allow for dislocation and adequate exposure of the humeral head so both anterior and posterior lesions can be accessed. The humeral head is dislocated with external rotation, adduction, and extension of the limb. Both the HilleSachs and reverse HilleSachs lesions should be adequately visualized and accessible at this point before proceeding (Fig 2). If the posterior HilleSachs lesion cannot be properly accessed with maximal external rotation, the inferior capsule may have not been adequately released.
The lesions on the humeral head are prepared into flat surfaces with a sagittal saw and burr. Bone wax is used to fill each defect to replicate the native anatomy (Fig 3). The anterior reverse HilleSachs defect is first filled with bone wax using the medial articular cartilage    and lateral lesser tuberosity as guides to judge the appropriate height of the patient's native humeral head. The bone wax is used as a template to harvest the same size wedge from the frozen proximal humeral osteochondral allograft. On the back table, the bone wax template wedge is measured across all dimensions and the allograft is marked for planned cuts to harvest the same size wedge. Clamps can be used by an assistant to maintain control and stability of the allograft while cuts are made with the sagittal saw.
The osteochondral allograft wedge is then provisionally held in place in the anterior reverse HilleSachs lesion with 2 k-wires and then definitively fixed with 2 cannulated headless compression screws (Acutrak headless compression screw system; Acumed, Hillsboro, OR). Care is taken to ensure the screw is recessed from the articular surface of the allograft wedge (Fig 4). This process is then repeated for the posterior HilleSachs lesion (Fig 5). Intraoperative fluoroscopy can be obtained to confirm restoration of anatomy of humeral head (Fig 6).
After completion of allograft wedge fixation, the subscapularis is repaired. If the subscapularis tendon is not able to reach its insertion onto the lesser tuberosity with relative ease, then the tendon may need to be mobilized from the capsular tissue and middle glenohumeral ligament in order to gain more excursion. Transosseous suture repair is performed by creating three transverse tunnels through the lesser tuberosity with a 2.0-mm drill. A high tensile strength #2 suture is passed through each tunnel and the medial limb of each suture is passed through the subscapularis tendon in modified MasoneAllen configuration. The corresponding suture limbs are tied together completing the subscapularis repair.
Advantages and disadvantages (Table 1), as well as pearls and potential pitfalls (Table 2), of this technique are summarized.

Discussion
Anterior and posterior glenohumeral instability are among the most common pathologies referred to orthopaedic surgeons. 9 Various arthroscopic and open treatments have been extensively reported for instability with bipolar bone loss, which have generally demonstrated good patient-related outcomes and low recurrence. 10 Locked anterior and posterior dislocations with large HilleSachs and reverse HilleSachs lesions can be treated with shoulder arthroplasty. 11 However, for young patients, in whom native anatomy restoration is prioritized, treatment with bony augmentation procedures with osteochondral allograft reconstruction has demonstrated favorable outcomes. 12 Allograft reconstruction can restore the joint to being on-track, thereby reducing risk of subsequent dislocations. 13 Patients with bipolar bone loss are disproportionately predisposed to greater rates of recurrent dislocation, necessitating distinct treatment paradigms. As bony augmentation treatment options evolve for both anterior and posterior humeral lesions, 14 the ability of surgeons to treat concomitant anterior and posterior lesions has dramatically increased, although it has not been previously described.
Concerns with extensive allograft reconstruction of the humeral head are lack of healing at the interface of the allograft with the native humerus, as well as the potential for collapse of the articular surface or graft resorption. For the patient described in this Technical Note, radiographs at 6 months have shown no evidence of collapse and do demonstrate incorporation of the allograft (Fig 6). The currently described technique does not limit the potential for future arthroplasty reconstruction options if these adverse outcomes are encountered while offering joint preservation and function in a younger patient.
In this technique, we present an anatomic reconstruction option for the young patient with large concomitant HilleSachs and reverse HilleSachs lesions to preserve native anatomy. Although shoulder arthroplasty may serve as a treatment option for bone loss, the loss of function and need for eventual revision arthroplasty in young patients present significant problems in this treatment paradigm. Therefore, young patients with significant anterior and posterior humeral bone loss from bidirectional instability may most benefit from attempted restoration of native joint anatomy with this technique.  Not properly identifying and coagulating the anterior humeral circumflex vessels during exposure at the inferior aspect of the subscapularis tendon can lead to excessive bleeding that can be difficult to control. Inadequate release of the inferior capsule may hinder access to the posterior HilleSachs lesion even with positioning the limb in maximal external rotation.